Set restrictions on packet_size, as per ISO-11172 / H-222 specifications
(max packet size should fit in 13 bits as a kB value, so 1<<23, plus the
header which is 10 bytes), and as per mpegenc.c internal assumptions
(min packet size is 20 bytes). See "[PATCH] make packet_size in
AVFormatContext unsigned" thread.

Originally committed as revision 19215 to svn://svn.ffmpeg.org/ffmpeg/trunk

idct_dc for VC-1/WMV3 decoder; ~11% faster decoding overall.
Includes mmx2 asm for the various functions.
Note that the actual idct still does not have an x86 SIMD implemtation.
For wmv3 files using regular idct, the decoder just falls back to simple_idct,
since simple_idct_dc doesn't exist (yet).

Originally committed as revision 19204 to svn://svn.ffmpeg.org/ffmpeg/trunk

Fix cast of byte buffer to uint32 that was disregarding alignment
requirements.
Now calculates crc byte at a time until aligned, then continues with uint32
optimized calculation.
This fixes crashes during mlp decoding on sparc (at least, maybe others).

Originally committed as revision 19160 to svn://svn.ffmpeg.org/ffmpeg/trunk